The present invention relates to a processing reactor and, more particularly, to a processing reactor for the thermal processing and chemical deposition of thin film applications on a substrate, such as a semiconductor wafer, in which chemical reactants are excited prior to injection into the reactor""s processing chamber to provide better control of the substrate processing conditions and, further, to enable new semiconductor device applications.
Several processing steps of semiconductor substrates involve chemical reactions at elevated temperatures. Heretofore, control of the deposition and annealing processes has been achieved by controlling the gas flow and pressure and, further, the wafer temperature. Various methods have been developed for measuring the temperature of a substrate during processing in order to improve the control of the various processes. For example, commonly assigned U.S. Pat. No. 5,814,365 discloses an improved reactor and heater which heats the substrate uniformly and, further, which provides for a temperature measurement device that enhances the control of the heating process to enhance the various semiconductor processes, including film deposition and etching, annealing, heat treating, and the like, and an improved gas injector which further enhances the control of the various processes. The disclosure of U.S. Pat. No. 5,814,365 is incorporated by references herein in its entirety. However, the elevated temperatures associated with the thermal processing and chemical deposition processes sometimes limit the device application and, further, may cause instability in already deposited films.
Consequently, there is a need for a processing reactor which can deliver reactant gases in a manner to enhance the deposition process and, further, in a manner to reduce the processing temperature so as to enable new device applications and retain the stability of already deposited films.
The present invention provides a processing reactor with an improved gas injection system. The gas injection system permits reduced process temperatures and, further, enhances the rate of deposition in some applications. In addition, the gas injection system enables new device applications in the processing reactor.
In one form of the invention, a reactor for processing a semiconductor substrate includes a reactor housing, which defines a processing chamber and is adapted to support a semiconductor substrate, and at least one gas injection assembly. The gas injection assembly injects at least one gas into the processing chamber and onto the substrate and is adapted to ionize the gas injected into the processing chamber to increase the reactivity of the gas with the substrate to thereby enhance the processing of the semiconductor substrate.
In one aspect, the gas injection assembly includes a plasma generator which ionizes the gas into a gas plasma. Preferably, the plasma generator ionizes the gas exteriorly of the processing chamber to isolate the substrate from the plasma generator. In preferred form, the plasma generator generates an electromagnetic field for ionizing the gas into the gas plasma.
In another aspect, the gas injection assembly includes a gas injection tube for delivering the ionized gas into the processing chamber. The injection tube preferably includes a plurality of orifices through which the ionized gas is delivered into the processing chamber. In preferred form, the gas injection tube comprises a quartz tube. In further aspects, the gas injection assembly further includes a plasma generator for ionizing the gas into gas plasma. The injection tube injects the ionized gas from the generator into the processing chamber. In preferred forms, the gas injection assembly further includes a supply tube in communication with the injection tube, which delivers gas to the injection tube. The plasma generator ionizes the gas into a gas plasma in the supply tube. Preferably, the plasma generator includes a generator tube in communication with the supply tube and generates an electromagnetic field in the generator tube to ionize the gas flowing into the supply tube into the gas plasma. For example, the supply tube may have a larger diameter than the generator tube such that the gas undergoes dissociation and ionization within the supply tube.
In other aspects, the gas injection assembly includes at two gas injection tubes, with one of the gas injection tubes injecting a first gas into the processing chamber and a second of the gas injection tubes injecting a second gas into the processing chamber. The gas injection assembly ionizes at least one of the gases into a gas plasma for injection into the processing chamber.
According to another form of the invention, a reactor for processing a semiconductor substrate includes a reactor housing, which defines a processing chamber and is adapted to support a substrate in the processing chamber, a plasma generator for ionizing at least one gas into a gas plasma, and at least one gas injector for injecting the ionized gas into the processing chamber and onto the substrate for processing the substrate.
In one aspect, the plasma generator includes a generator tube and a coil which induces an electromagnetic field in the generator tube to ionize the gas flowing through the generator tube with the generator tube directing the ionized gas into the gas injector for injecting into the processing chamber.
In other aspects, the housing includes a cover with a gas injector being supported in the cover. Preferably, the plasma generator is supported by the cover exteriorly of the processing chamber to isolate the substrate from the plasma gas generator.
In other aspects, the reactor includes at least two gas injectors for injecting at least one gas into the processing chamber. Preferably, the gas injectors are isolated from each other to avoid contamination.
In another form of the invention, a method of processing a semiconductor substrate includes providing a processing chamber, supporting the substrate in the processing chamber, ionizing a gas and injecting the ionized gas into the processing chamber under the substrate for processing the semiconductor substrate.
Preferably, the gas is ionized into a gas plasma, for example by applying an electromagnetic field, such as a radio frequency field, to the gas. In other aspects, the substrate may be cleaned with the ionized gas.
As will be understood, the reactor of the present invention provides numerous advantages over the prior known reactors. By ionizing the reactant gases, the gases are more reactive with the semiconductor substrate. As a result, the temperatures normally associated with processing such substrates can be significantly reduced. With reduction in processing temperatures, the stability of already deposited films can be retained and, furthermore, new device applications can be achieved. These and other objects, advantages, purposes and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings.